BRAINCAKEEvidence for the Movement of Water Through Xylem
Several simple experiments show that water moves up the plant through the xylem, and that it is pulled up under tension.
Dye experiments. If a cut celery stalk or a white flower is placed in water containing a coloured dye such as eosin, the dye moves up the stem. When a thin cross-section of the stem is cut and viewed, only the xylem is stained. This shows that water travels in the xylem.
Ringing experiments. If a ring of bark is removed from a woody stem, the phloem is removed but the xylem, which lies deeper, is left intact. The leaves above the ring do not wilt, so water must still be moving up through the xylem.
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Key terms in this lesson
- cohesion-tension theory
- The theory that water is pulled up the xylem as a continuous column, held together by cohesion between water molecules, driven by transpiration.
More in Transport in Plants
- Xylem and Phloem
- Xylem
- Phloem
- Root Hair Cells
- Symplast Pathway
- Apoplast Pathway
- Transpiration
- Cohesion-Tension Theory
All 21 lessons in Transport in Plants · All Edexcel AS-level Biology topics